This type of vehicle seat includes a woven knitted fabric of a net shape that is tightly stretched on a seat surface instead of a pad material made of foamed resin for the purpose of reducing weight, improving air permeability, etc., and is referred to as a so-called net seat. The net seat of the related art utilizes a net of single-layer structure configured by one sheet of woven knitted fabric. In the net seat of the related art, there is a problem in cushion property (level of sitting comfort).
JP-A-2002-233437 aims to improve the cushion property (level of sitting comfort) by tightly stretching a three-dimensional woven knitted fabric having a surface-layer-side base fabric, a back-layer-side base fabric, and an intermediate layer that three-dimensionally connects the surface-layer-side base fabric and the back-layer-side base fabric. The three-dimensional woven knitted fabric employs the base fabric made of the same woven knitted fabric for both surface and back layer sides, and an almost entire surface is formed in a uniform three dimensional structure along an edge portion thereof. In addition, a locking member is sewed to an end portion of the three-dimensional woven knitted fabric including the surface-layer-side base fabric. The three-dimensional woven knitted fabric is tightly stretched by locking the locking member to a wire provided along the seat frame.
In this type of net seat, a load from a passenger is applied as tension acting in a surface direction to the three-dimensional woven knitted fabric. However, in JP-A-2002-233437, the surface-layer-side base fabric is sewed to the locking member together with the back-layer-side base fabric. Since the surface-layer-side base fabric and the back-layer-side base fabric are locked to the seat frame, if the load is applied from the passenger to the three-dimensional woven knitted fabric, the tension also acts on the surface-layer-side base fabric in the surface direction, so that the surface-layer-side base fabric is tensed. This causes the cushion property of the three-dimensional woven knitted fabric to deteriorate, thereby making the level of sitting comfort worse.
Furthermore, since the same base fabric is used for both the surface and back layer sides, there is a problem in that the surface-layer-side base fabric, to which the load is preferentially applied from the passenger, is tensed more than the back-layer-side base fabric. Also, since the intermediate layer is formed along the edge portion of the three-dimensional woven knitted fabric and lacks flexibility at the edge portion, when the locking member is locked to the seat frame, uneven tension may be applied to the edge portion or creases may be formed at the edge portion.